In general, an inkjet printhead has a housing or body that defines an interior filled with one or more inks. To prevent back pressure build-up during printing, each compartment contains a lung or a foam insert and an air diffusion vent that fluidly communicates the interior to atmospheric pressure. Often times, the air diffusion vent embodies a circuitous or torturous path in the form of a serpentine channel that snakes from a hole fluidly connected to the interior, and formed through a thickness of the housing, to a terminal end thereof. A label, or other covering, typically lays over the hole and portions of the air diffusion vent, but not the terminal ends, to slow the effects of ink evaporation.
If a printhead is placed in a low atmospheric condition (i.e. shipping), it is possible that ink can leak out of the vent hole. For example, during shipping on an airplane, printheads are exposed to low atmospheric conditions (i.e. flying at an altitude of 19000 ft, the atmospheric pressure is reduced by ½ compared to sea level altitude) which can cause leaks. In order to prevent such leaks, a sheet of hydrophobic film material may be placed on the cartridge lid so as to cover the air diffusion vent holes.